There is very interesting solution to that.
PROJECT2{3} 3, 270, 3+32, 2+8, 0, 0, 0, 0, PARAMETERS yourParameter=1, yourParameter2=2
When ArchiCAD generates 2D drawing, it applies the value of given parameters, that can control in 3D script visibility of different parts.
This is going to work, only if
yourParameter
is set in parameters list, not in GDL script only.